Different types of User Equipment, UE, performance requirements are specified in the standard. In order to ensure that UE meets these requirements, appropriate and relevant test cases are also specified. During the tests all the downlink radio resources are not typically needed for the user under test. In practical circumstances several users receive transmission simultaneously on different resources in a cell. To make the tests as realistic as possible these remaining channels or radio resources should be transmitted in a manner that mimics transmission to other users in a cell.
The objective of UE performance verification (or the so-called UE performance tests) is to verify that UE fulfils the desired performance requirements in a given scenario, conditions and channel environment. By desired performance requirements it is meant those specified in the standard or requested by an operator or by any prospective customer. The performance requirements span a very vast area of UE requirements, such as:                UE RF receiver requirements e.g. receiver sensitivity        UE RF transmitter requirements e.g. UE transmit power accuracy        UE demodulation requirements e.g. achievable throughput        Radio resource management requirements e.g. handover delayWe can classify the UE verification into two categories:        Verification in lab        Verification in real networkVerification in Lab        
In the verification in lab the base station is emulated by test equipment, which is often termed as system simulator. Thus all downlink transmission is done by the test equipment to the test UE. During a test all common and other necessary UE specific control channels are transmitted by the test equipment. In addition a data channel, e.g. PDSCH in E-UTRAN, is also needed to send necessary data and configure the UE. Furthermore typically a single UE is tested at a time. In most typical test cases the entire available downlink resources are not used by the UE. However to make test realistic the remaining downlink resources should also be transmitted to one or multiple virtual users.
In OFDMA system the transmission resources comprises of time-frequency resources called resource blocks, which are sent with some transmit power level, as described in more detail below. This type of resource allocation to generate load in OFDMA will be referred to as OFDM channel noise generator (OCNG) in the following. Thus OCNG is sent to a plurality of virtual users for loading the cell.
Verification in Real Network
These types of tests are demanded by the operators and are performed in a real network. The test may comprise of single or multiple UEs. Prior to the network roll out or in an early phase of deployment the traffic load is typically very low. In classical tests the cell load is generated by increasing transmission power on one or more common channels. However operators are now increasingly demanding the network vendors to generate cell load in realistic fashion for performing tests. This means resources, which are not allocated to the test users should be allocated to the virtual users emulating load in the cell. Thus either all or large part of available resources i.e. channels, transmit power etc is used in the tests. This requires base station to implement the ability to transmit remaining resources in order to generate load. Thus for OFDMA (i.e. in E-UTRAN) OCNG is also deemed to be implemented in an actual base station.
Noise Generation in WCDMA for UE Performance Verification
In WCDMA orthogonal channel noise simulator (OCNS) is used to load cells in the test. The OCNS is implemented in both test equipment and also possibly in the base station. In the former case it is standardized in TS 25.101 and TS 25.133 for each type of test or same for similar tests. The OCNS comprises of channelization code and relative power. In a CDMA system the position of channelization code in a code tree is sensitive to intra-cell interference. Therefore more careful selection of codes for OCNS and their power levels is needed. An example of OCNS from TS 25.101 for UE demodulation tests is quoted below:
TABLE 1DPCH Channelization Code and relative level settings for OCNS signalRelative LevelChannelizationsetting (dB) (NoteCode at SF = 1281)DPCH Data (see NOTE 3)2−1The DPCH data for each11−3channelization code shall be17−3uncorrelated with each other and23−5with any wanted signal over the31−2period of any measurement. For38−4OCNS with transmit diversity the47−8DPCH data sent to each antenna55−7shall be either STTD encoded or62−4generated from uncorrelated69−6sources.78−585−994−10125−8113−61190NOTE 1: The relative level setting specified in dB refers only to the relationship between the OCNS channels. The level of the OCNS channels relative to the Ior of the complete signal is a function of the power of the other channels in the signal with the intention that the power of the group of OCNS channels is used to make the total signal add up to 1.NOTE 2: The DPCH Channelization Codes and relative level settings are chosen to simulate a signal with realistic Peak to Average Ratio.NOTE 3: For MBSFN, the group of OCNS channels represent orthogonal S-CCPCH channels instead of DPCH. Transmit diversity is not applicable to MBSFN which excludes STTD.E-UTRAN Downlink Transmission
In E-UTRAN Orthogonal Frequency Division Multiplexing (OFDM) technology is used in the downlink, whereas DFT based pre-coded OFDM is used in uplink. In E-UTRAN the cell transmission bandwidth is divided into several time-frequency resources. Most of these resources comprise of resource blocks, which comprises of 0.5 ms (time slot) in time domain and 12 sub-carriers each of 15 kHz in frequency domain. However some of the resources used for common channels e.g. SCH channel (primary and synchronization sequences) or reference symbols are transmitted over one or more OFDM symbol in time domain in each sub-frame. Some other control signals such as PCFICH, PHICH and PDCCH are also sent in specific OFDMA symbol in each sub-frame. The resource blocks are used for transmitted user data or some control signaling e.g. paging, system information etc.
Furthermore E-UTRAN is a pure packet data designed cellular system, in which transmissions of user data in uplink and downlink always take place via shared channels. As similar to HSPA in UTRAN, the UE monitors physical downlink control channels (PDCCH) in order to access UE dedicated user data on the physical downlink shared channel (PDSCH) and the network assigns uplink scheduling grants to the UE on demand basis for uplink transmission via the physical uplink control channel (PUCCH) and the physical uplink shared channel (PUSCH). Error detection is provided on transport blocks and control payloads through Cyclic Redundancy Check (CRC) on PDSCH and PUSCH, and HARQ operations ensure efficient re-transmissions.
In E-UTRAN, no downlink transmit power control (TPC) has been specified and uplink TPC commands are embedded in the control payload mapped to PDCCH, which are sent occasionally or frequently by the E-UTRAN base station (eNodeB).
Downlink Physical Signals and Channels in E-UTRAN.
The physical layer signals and channels in E-UTRAN downlink are:                Physical layer signals, i.e. reference signal (pilots) and synchronization signals;        Physical broadcast channel (PBCH);        PDCCH and PDSCH;        Physical control format indicator channel (PCFICH); and        Physical HARQ indicator channel (PHICH)        
Following observations can be made:                Physical layer signals and PBCH are transmitted periodically;        Error detection via CRC of transport blocks mapped to PBCH and PDSCH, and of control data mapped to PDCCH;        Some uplink transmissions shall result in downlink responses through the physical channels PDCCH and PHICH.        
The cell load is generated by OCNS in WCDMA, UTRAN TDD or other CDMA systems. The same concept is not needed in E-UTRAN since radio interface is based on OFDMA technology, which is less sensitive to intra-cell interference. But there is still some leakage across the sub-carriers contributing to intra-cell interference due to transmitter and receiver imperfections. However inter-cell interference is not orthogonal and therefore it can still be considerable in OFDMA like in CDMA. Currently no rules on how to generate cell load for performing UE performance test are available for OFDMA systems.